The Unit continued work on the development of new vaccines against Shigella flexneri and Bacillus anthracis, products are currently in clinical trials. A production and purification procedures for recombinant Pseudomonas aeruginosa exotoxin A was developed and gram quantities of the protein were made. This protein was used for the preparation of a conjugated vaccine by conjugating the protein to the bacterial polysaccharide. A production and purification procedure for obtaining inactivated protective antigen from Bacillus anthracis was established and gram quantities of this protein were made. This anthrax vaccine is being studied by using several different formulations: formaldehyde treated, formaldehyde treated with alum, alum alone, and untreated protein. Additionally, conjugating the protective antigen with the anthrax capsule is currently being prepared for clinical studies. Several proteins were prepared for evaluation as a potential candidate for conjugation, among them recombinant toxin A of Clostridium difficle and recombinant diphtheria toxoid. [unreadable] [unreadable] The Biotechnology Unit also produced large quantities of experimental recombinant malaria transmission blocking vaccine from Pichia pastoris, this work was done in collaboration with the Malaria Vaccine Development Unit of NIAID. The Unit was also involved in improving the production procedure of plasmid DNA, evaluating different host microorganisms. Significant increase in specific production was achieved by replacing the current E. coli production strain with a genetically modified strain.